ABSTRACT

We request moderately long (100 ksec) observations of the two prototypical ultraluminous infrared galaxies (ULIRG) Mrk 231 and Arp 220 (infrared luminosities greater than 10^12 solar luminosities). The primary goal is to search for heavily obscured (i.e., Compton-thick), X-ray luminous AGN in these two galaxies, by looking for the spectral signatures of reflection-dominated X-ray sources. Detection of such AGN (an example of which is seen in the ULIRG NGC 6240) would have major implications for the dominant energy source in this important class of galaxies.